The maintenance of normal architecture of human skin and other tissues demands the elaboration and precise regulation of the enzyme collagenase, which is specifically required to initiate collagen degradation. The purpose of these investigations is to define the structure, biochemical properties, mechanisms of action, and the systems of regulation of human skin collagenase. Human skin fibroblasts synthesize procollagenase, which is secreted as a set of two proteins, differing in molecular weight by about 5,000 d. In order to understand how the enzyme functions in the precisely controlled processes of collagen metabolism, the primary sequence of human skin procollagenase will be established, by means of classical sequence methodology and recombinant DNA techniques. The differences in function between the normal enzyme and the mutant recessive dystrophic epidermolysis bullosa collagenase will be defined by a detailed structural comparison of the two. The enzymology of normal human skin collagenase will be compared to that of other human and animal collagenases with respect to collagen type specificity, kinetic parameters, binding characteristics, and methods of catalysis. A specific inhibitor of human skin collagenase, produced by fibroblasts, has been purified, and its properties, mechanism of inhibition, and regulation of its activity will be studied. Production of a monospecific antibody will allow development of an immunoassay, to quantitate and localize inhibitor production, and to determine whether human skin collagenase and its specific inhibitor are co-regulated or independently controlled. We are also concerned with the mechanisms whereby procollagenase is activated in vivo. An activator of procollagenase has been purified from human skin, and an effort will be made to elucidate its mechanism of action, cellular location, and the means for regulating the activity of this key molecule. These studies will result in further understanding of the collagenase enzyme system, which controls events of major importance in normal and pathologic physiology, and will clarify its role in recessive dystrophic epidermolysis bullosa, cutaneous hamartomas, and tumor invasiveness.